Beam forming is often used to extend the range of wireless communication links by focusing radio frequency (RF) energy along a chosen “direction” instead of in “all” directions creating a link budget gain and an increase in range. With respect to an RF transmitter, beam forming may be accomplished through the use of a plurality of antennas transmitting two or more RF signals. The antennas allow the transmitted RF energy to be steered or “beam formed”. Similarly, an RF receiver may use a plurality of antennas to selectively receive RF energy. Thus, beam forming requires that the transmitter and the receiver know the relative positions of each other to correctly direct the RF energy. The beam forming at the transmitter and the receiver provide a signal processing gain compared to omnio-directional transmission and reception which in turn may increase the signal-to-noise ratio within a communication system.
There are many well-known methods to determine relative positions of transmitters and receivers, such as those set forth in the IEEE 802.11n specification. Beam forming works well when the transmitter knows the “direction” of the receiver. However, there are scenarios where information, such as control information, needs to be exchanged between transmitter and receiver before the transmitter knows the direction of the receiver (and thus before beam forming may be reliability employed). Also, sometimes certain information needs to be broadcast to all the receivers in the vicinity, so that transmitting the signal along just one direction may be insufficient since the receivers may be distributed in many directions. Many communication protocols have surmounted this challenge by defining an alternate signaling technique, usually referred to as Control PHY signaling. While the normal data exchange is done with beam forming using the “normal” PHY, the control information exchange, which typically does not make use of beam forming, is done using Control PHY signaling.
One problem with this approach is more noticeable when a Physical transport operates at a relatively high frequency, for example around 60 GHz. At these frequencies, there is relatively high propagation loss and, even with beam forming, a range of only ten meters may be achieved. Without beam forming, the range may drop to much less than ten meters. Methods and apparatus are needed that can be used for control information exchange where the range is not substantially diminished when traditional beam forming techniques may not be available.